Stare at the numbers. Especially the first two. First one is -11. Second is . Let's guess you keep multiplying. . Smells correct, let's confirm with the last one: . I think we found a pattern. Each element is 7 times the previous one. With some practice you can just write the function, else let's divide by -11 away and let's see what we get:
. Basically, the exponent is 1 less than the value we're evaluating the function. That leads tho the following
